the possible influence of the nao on the mediterranean outflow water path in the north atlantic...
TRANSCRIPT
The Possible Influence of the NAO on the Mediterranean Outflow Water Path in the North
Atlantic
Alexandra Bozec1, Eric Chassignet1, George Halliwell2, Zulema Garraffo2, Susan Lozier3 and Nicole M. Stewart3
Hycom meeting, April, 24-26
1Center for Ocean-Atmospheric Predictions Studies, Florida State University, Tallahassee, FL, USA2Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, USA3Division of Earth and Ocean Sciences, Duke University, Duke, NC, USA
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Outline
• Observations
• Parameterization of the MOW tongue in HYCOM
• Results in the 1/3° resolution HYCOM
• Future work
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From Lozier and Stewart, 2006
Observations
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NAO+ 1985-1994
Increasing salinity anomaly
NAO- 1960-1969
On σ1= 32.10; at MOW core
Lozier and Stewart, 2006
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Weak westerlies: NAO- Strong westerlies: NAO+
Lozier and Stewart, 2006
Contraction Expansion
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Comparison of the outflow representation in different model resolution of the ATL
• 2° simulation: ATLc2.00 (2deg-PY)– Initial state: GDEM3 climatology – Forcing: ECMWF-ERA40 climatology
• 1°x0.5°: ATLc1b.00 (extracted from global configuration) (1deg-med and 1deg-PY) (Y. Yang and T. Ozgokmen)
– Initial state: GDEM3 climatology – Forcing: ERA40 climatology
• 1/3° : ATLc0.32 (0.32deg-PY)(Z. Garraffo and G. Halliwell)
– Initial state: GDEM3 climatology – Forcing: interannual NCEP 1948-2003
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MOW in HYCOM
Q1,1,S1Q2,2,S2
E P R• The Price and Yang model (Price and Yang,
1998) is used as a boundary condition to prescribe the outflow in the HYCOM ocean model. Specified parameters are :– Med. Surf. Fluxes
• E-P-R over Mediterranean• Net Heat flux over Mediterranean
• Specified Atlantic Ocean Water Properties 1, S1 of Gibraltar inflow water• Density, salinity of entrained interior
water at shelf-slope break
• P-Y Model Output• Gibraltar outflow , S2, Q2
• Entrained interior water transport• Final product water , S3, depth,
transport(Q3)
Q3,3,S3
(implemented in HYCOM by George Halliwell)
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Model Grids
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Price and Yang in ATLc2.00
Simulation 2° (climatology : ERA40 forcing)
2deg-buffer: with buffer zone in the Gulf of Cadiz
2deg-PY: with Price and Yang
Depth: 1000m
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Simulation 1°x0.5° (climatology: ERA40 forcing)
1deg-med: with the Mediterranean Sea
1deg-PY: with Price and Yang
013 014
Price and Yang in ATLc1.00
Depth=1000m
1deg-med 1deg-PY
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Price and Yang in 1/3°ATL: 0.32deg-PY
34.2 36.2 34.2 36.2
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First results: 0.32deg-PYC
ON
TR
AC
TIO
NE
XP
AN
SIO
N
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Conclusion/summary
• The mechanism of expansion/contraction found in
the observations is also present in the 1/3° HYCOM
interannual simulations.• Future work : Can we find a relation between the
NAO and the salinity anomalies in the Rockall Trough
as in the observation ?
If yes, can we develop a physical explanation for the
expansion/contraction mechanism as a function of
NAO?
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Different representations of the outflow